This section provides background information related to the present disclosure, which is not necessarily prior art.
Heating, ventilation, and air conditioning (HVAC) systems for vehicles often use a side face bleed to control window fogging in a foot mode. Recently there has been a trend towards requiring a similar bleed, but from the side-window defrost outlets. Existing HVAC system architectures are designed to support the face bleed (using air paths built into the cases), so architecture changes are required to support the trend toward side-window defrost outlet airflow bleeds in a foot mode. For example, some systems use a large sub-defrost door to block the main defrost outlet, but this is a costly and complex solution that requires additional parts and design resources to implement. Furthermore, such doors are prone to noise issues (e.g., whistles due to small openings), vibration issues due to shaft strength, and make it difficult to get precise main defrost bleed values. The sub-defrost door also blocks airflow even in the open position, and hence impacts overall performance.
The present teachings advantageously provide for an improved HVAC system that addresses the issues with current systems. For example, the HVAC system according to the present teachings advantageously eliminates the small door openings currently used to provide defrost bleed conditions, which are difficult for kinematic systems to control. The present teachings also allow for simplified HVAC case structures, and the airflow doors according to the present teachings can fit in an area that is sized similar to existing defrost door designs. The present teachings provide for numerous additional advantages as explained herein, and as one skilled in the art will recognize.